1. Field of Invention
This invention is directed to systems and methods for maintaining and/or enhancing operation of fluid ejection systems.
2. Description of Related Art
Fluid ejection systems, such as drop on demand liquid ink printers, use various methods to eject fluids, including but no limited to piezoelectric, acoustic, phase change, wax based and thermal systems. These systems include at least one fluid ejector from which droplets of fluid are ejected towards a receiving medium, such as a sheet of paper. A channel is defined within each fluid ejector. The fluid is disposed in the channel. Droplets of fluid can be expelled as required from orifices or nozzles at the end of the channels using power pulses.
In some fluid ejection systems, such as, for example, drop on demand thermal ink jet printers, a pressurized reservoir of ink is connected to a plurality of ink channels and, subsequently, the nozzles, via a fluid supply manifold. The fluid supply manifold contains internal, closed walls defining a chamber with an ink fill hole. The fluid supply manifold receives ink from the ink reservoir and distributes it via internal passageways to the plurality of ejector channels. A plurality of sets of channels and associated fluid supply manifolds can be defined within a single fluid ejection system or printhead. One or more filters can be situated within the fluid supply manifold and/or entrance to each channel. The filters are designed to collect solidified waste fluid and other contaminants, bubbles, debris, residue and/or deposits or the like that can negatively impact the fluid ejector.
U.S. Pat. No. 4,639,748 to Drake et al. discloses an internal, integrated filtering system and fabrication process for an ink jet fluid supply manifold. Small passageways are defined within the fluid supply manifold to deliver ink to a plurality of ink channels. Each of the passageways has smaller cross-sectional flow areas than the ink channels. Therefore, any contaminating particle in the ink that would have passed to the ink channels will be filtered or stopped by the passageways before entering the ink channels.
In drop-on-demand thermal ink jet printers, a heating element normally located in the ink channel causes the ink to form bubbles. By applying a voltage across the heating element, such as a heater transducer or resistor, a vapor bubble is formed. The bubbles force the droplets of ink from the nozzle onto the sheet of receiving medium. The channel is then refilled by capillary action from the ink reservoir via the fluid supply manifold.
While ejecting fluid, fluid drawn from the fluid reservoir is directed through the passageways of the fluid supply manifold to each ejector channel. Contaminants, bubbles, debris, and/or residue located in the fluid reservoir can travel to the ejector channels. Filters within the fluid supply manifold and/or design techniques of the fluid supply manifold often trap the contaminants, bubbles, debris, and/or residue before they reach the fluid channels. However, some contaminants, bubbles, debris, and/or residue can reach the inlet of the ejector channels. Just as contaminants, bubbles, debris, residue, and/or deposits can accumulate on the face of the ejector head, thus clogging ejector nozzles and resulting in a deleterious effect on ejection quality, so too does the accumulation of contaminants, bubbles, debris, and/or residue at the inlet of the ejector channels negatively impact the ejection quality.
Removing solidified waste fluid and other contaminants, bubbles, debris, residue and/or deposits or the like from the face of the ejector head can be accomplished using any number of available methods, including, but not limited to, using a wiper blade, using a washing unit, and any combination of wiping and washing. While these have proven effective in removing solidified fluid or minute particles from the face of the ejector head, similar methods for clearing ejector channel inlets are not available. As a result, the ejection operation is diminished and slowed because several partial ejection swaths are required to cover the defects.
The inventor has determined that ejecting the fluid droplets, such as ink, from the ejector nozzle results in a back pressure within the ejector channel. This back force is directed out the channel inlet, often ejecting any residual fluid remaining in the channel back towards the fluid supply manifold.
This invention provides systems and methods for maintaining fluid ejection channels.
This invention separately provides systems and methods that remove at least some debris from a channel inlet.
This invention separately provides systems and methods for driving a fluid ejection system using a fluid ejection sequence.
This invention further provides systems and methods that move to a less harmful position at least some debris that interferes with proper fluid ejection from the ejector channels of the fluid ejection system using the fluid ejection sequence.
In various exemplary embodiments of the systems and methods according to this invention, at least some of a plurality of fluid ejectors are fired in a sequential pattern. In various exemplary embodiments, firing a fluid ejector results in a back pressure wave that moves debris, residue, contaminants, deposits or the like back out of the inlet of the fired fluid channel and/or any filter elements positioned on or near the inlet. In various exemplary embodiments, sequentially firing the fluid ejectors causes the back-ejected debris, residue, contaminants, deposits or the like within the fluid supply manifold to move along the direction of the firing sequence. In various exemplary embodiments of the systems and methods according to this invention, the moved contaminants, bubbles, debris, residue and/or deposits or the like can be deposited into locations within the fluid supply manifold that are not associated with operative fluid ejector channels.
In various exemplary embodiments of the systems and methods according to this invention, the fluid ejectors are fired in a sequential pattern within blocks of the fluid ejectors. For example, a fluid ejector head with, for example, 120 fluid ejectors can fire 1 out of every 20 fluid ejectors. Therefore, during a first period of the sequence, ejectors at positions 1, 21, 41, 61, 81 and 101 fire. Each fluid ejector is fired at least one time, and, in various exemplary embodiments, is fired multiple times, such as, for example, up to 100 times, before the next fluid ejector in the sequence is fired. Then, during a second period of the sequence, the fluid ejectors at positions 2, 22, 42, 62, 82, and 102 fire. Groups of fluid ejectors are fired in this manner until all 120 of the fluid ejectors have fired. This moves any debris, residue, contaminants, deposits or the like within the fluid supply manifold in the direction of firing, i.e., from position 20x+1 to position 20x+20.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.